Tamron 90mm 2.8 Macro

The Tamron 90mm 2.8 macro lens.
I think all macro lenses are just a normal telephoto lens with a built in extension tube. This is because like all lenses attached with extension tubes, the aperture is smaller depending on the added extension. Same as the macro lens.

Autofocus (AF)
AF is not fast, but considering this being a macro lens with a longer focusing distance, I think it’s not too shabby.
There is a Full and Limit lock at the side. This will allow the AF to either go through the entire focusing distance or focus only the limited distance. If the limit is set at infinity end, the AF will stop at 45cm. This would be the range for a normal lens. AF will be faster. If limit is locked at 1:1, then it is in macro mode. AF will go between 40cm to 29cm. This Full and Limit switch will also work with manual focus.

Closest Focusing Distance
Comparison of lens extension between infinity focus and closest focus.
(when you see the blue ring, the lens is in manual focus)

As you can see, the lens extends quite a bit.
Closest focusing distance is 29cm.
This will give you a 1:1 magnification ratio.
However, as with all macro lenses, it is not a constant f/2.8 lens.
As the lens goes to 1:1, it’s widest aperture is no longer f/2.8 but f/5.6
The smallest aperture is also not f/32 but f/64.